Rock-salt-like oxides

The implications are that conduction electrons confined to the inner-layer slab, in oxides with low d electron counts, may be more spatially screened from electron localizing effects such as chemical or structural disorder in the rock-salt-like slabs, as compared with conduction electrons in single-layer slabs. 

All of the alkaline earth oxides, MO, except one crystallize in the rock salt (NaCt) structure. What is the exception and what is the likely structure for it (Wells, A. F. Structural Inorganic Chemistry, 5th ed Oxford University Oxford, 1984.)... 

Sulfate is principally derived from the weathering of CaS04 minerals (gypsum and anhydrite) in sedimentary rocks. Some sulfate in rivers, however, comes from the weathering of magnesium sulfate salts in sedimentary rocks and from oxidation of sulfides (primarily FeS2. pyrite) in sedimentary and crystalline rocks. The latter process also liberates small amounts of the cations Ca2+, Mg2+, Na+, and K+ by reactions like ... 

Independently of Carpenter, Jeffery and Kipping [86] proposed a method for determining carbonates in rocks. In contrast to Carpenter s method they proposed to use a dilute solution of orthophosphoric acid to decompose the carbonates. The same method of determining gaseous products by decomposing salt-like derivatives of phosphoric acid was also used for determining carbon dioxide and nitrogen oxide in aqueous solutions of monoethanolamine [87]. 

Chlorine is a dense, greenish-yellow gas. Although it may be a gas or a liquefied gas, it can also be released from solid compounds that are oxidizers. Chlorine is not combustible however, it will support combustion just like oxygen. Chlorine does not occur freely in nature. It is found in compounds within the minerals halite (rock salt), sylvite, and camallite, and as the chloride ion in seawater. 

Thus, today Ruddlesden-Popper phases include complex oxides eontaining metals from groups 1,2, 13, 14 and 15 as well as transition (d- and 4f-) elements. The general formula of such oxides can be written as A0(AB03)n, where A means alkaline, alkali earth or rare earth element, while B is d-element, Al, Ga, In, Pb or Bi. This formula shows the main structural feature of this class of the layered perovskite-like eompoimds, that is the intergrowth of the perovskite blocks AMO3 (P) and rock salt blocks AO (RS) in a consequence -Pn-RS-Pn-RS-. In case of n = 00 the perovskite structure itself is obtained. Pigure 1 shows schematically the structure of the Ruddlesden-Popper phases (n=3) as eompared to the other types of the layered perovskite-like compounds. 

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